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This invention relates to improvements in slotted cable runway localizer antennas for the Instrument Landing System (ILS). It combines features of two earlier U.S. Pat. No. 3,577,197, May 4, 1971, Watts, Jr., xe2x80x9cSlotted Cable Localizer Antenna,xe2x80x9d (Ref.1), and U.S. Pat. No. 4,464,665, Aug. 7, 1984, Watts, Jr., xe2x80x9cSlotted Cable Antenna Structure,xe2x80x9d (Ref.2), to provide superior performance. An embodiment of this invention is described in a published paper: Watts, Jr. and Johnson, J., xe2x80x9cSlotted Cable ILS Localizer,xe2x80x9d Proceedings of the 10th International Flight Inspection Symposium, Seattle, Wash., June, 1998, (Ref.3).
This antenna radiates simultaneous sum and difference patterns carrying standard ILS reference (CSB) and deflection (SBO) components of the transmitted signal. The signal components from an ILS transmitter are supplied through an rf bridge (hybrid) to both ends of the slotted cable structure. Optional isolators inserted in the coaxial feed lines improve the impedance presented to the transmitter.
An object of the invention is to provide a slotted cable localizer antenna having improved efficiency and ease of construction. This is accomplished through a particular arrangement of parts, many of which are common copper plumbing fittings, together with other special parts to be described.